Add a select button to Manifest fields with mod_ids

For the inputs:

- Dependencies
- Optional Dependencies
- Incompatible Mods
- Load Before

a drop down / options button to select a mod in the "mods-unpacked" dir would be nice.

Locate the Manifest fields for Dependencies, Optional Dependencies, Incompatible Mods, and Load Before, then trace how available mods are discovered in the "mods-unpacked" directory. Add the requested selection control and verify that choosing a mod fills the relevant mod_id field.

Written by the indexing model from the issue text.